The invention relates to a blocking system for the medullary canal of a tubular bone in which a prosthesis shaft can be fastened with bone cement, with the blocking system having a blocking element which can be anchored in the medullary space prior to the introduction of the bone cement in order to prevent an advance of bone cement.
The previous teaching for the formation of the cement jacket about the shaft of a cemented in prosthesis starts from as uniformly thick a cement jacket as possible which completely surrounds the shaft, with at most a somewhat greater accumulation of bone cement being tolerated under the shaft end in order to compensate the fluctuations between the setting depth of a mechanical medullary space blocking and the penetration depth of the shaft end.
A mechanical medullary space blocking of this kind is described in the patent specification U.S. Pat. No. 4,293,962 with an associated setting tool. A similar medullary space blocking is shown by the patent specification U.S. Pat. No. 4,245,359 or U.S. Pat. No. 4,344,190 in which the material of the mechanical medullary space blocking can be decomposed in the body. A disadvantage of an arrangement of this kind consists in that relatively large drawing tensions can arise in the transition from the cement socket to the cement plug lying under the shaft end when the shaft moves slightly downwards within the hardened cement socket.